Work table

ABSTRACT

A work table is provided with a housing ( 10, 23 ) and a rotary element ( 11, 12, 24 ) mounted rotatably at the housing ( 10, 23 ) as well as with a locking device ( 22, 23, 26 ) for fixing the particular angle of rotation position of the rotary element ( 11, 12, 24 ) in relation to the housing ( 10, 23 ). To provide the work table with a fail-safe behavior the locking device ( 22, 23, 26 ) is released by a first actuating member when the energy supply is switched on and is activated by means of a restoring member when the energy supply is switched off. An additional actuating member may be provided to boost the locking force.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 of German Application DE 103 58 943.0-14 filed Dec. 15, 2003, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a work table with a housing and with a rotary element mounted rotatably at the housing as well as with a locking means for fixing the particular angle of rotation position of the rotating element in relation to the housing.

BACKGROUND OF THE INVENTION

Such a work table is disclosed, for example, in DE 202 02 998 U1. This work table has a round table mounted rotatably at a housing, which is called substructure in the document. Workpieces are clamped on the round table in the usual manner in order to subject them to machining, especially cutting. Consequently, the round table is a workpiece mount arranged rotatably at the housing. The workpieces mounted on the round table can be rotated by means of the round table driven by a rotating drive into predetermined positions favorable for the particular machining step and then machined.

Considerable forces, which must be diverted via the round table, act on the workpiece during the machining of workpieces, especially by milling, planing or the like. These forces apply a considerable torque on the round table, so that it may inadvertently rotate in relation to the housing. This is prevented by means of the locking means.

Motor-driven worm gear mechanisms were originally used as the rotating drive. These had the advantage of locking the particular angular position of the rotary element (round table) by means of a self-locking design. The worm gear mechanism was consequently also the locking means at the same time.

There has more recently been a change to providing the round tables with a so-called direct drive via a torque motor, as it is offered, for example, by the firm of Eberle. The possibility of locking the rotary element by means of self-locking is eliminated here. A clamping is therefore provided between the housing (substructure) and the rotary element (round table) in the work table according to DE 202 02 998 U1. A disk arranged at the round table is now clamped, and it is clamped such that the clamping is activated by admitting a pressurizing agent into hydraulic cylinders after the angular position of the round table has been set in relation to the housing.

The drawback of this procedure is that the clamping is released in case of failure of the pressurizing agent supply for the hydraulic cylinders. This may lead to an inadvertent rotation of the round table and consequently to a crash of the workpiece and even to a risk of injury to personnel due to breaking tools and/or workpieces.

Locking means similar to those described in DE 202 02 998 U1 are disclosed in U.S. Pat. No. 6,457,383 B1 and U.S. Pat. No. 6,001,145 A.

DE 195 15 085 C2 shows a locking means for a belt drive. Should a drive belt break, a spring-loaded locking lever is pivoted and it engages a locking wheel as a result. The locking lever can be pivoted back and the locking abolished by a cylinder.

In the locking means shown in DE 42 14 947 A1, a bar or shaft is clamped by means of a clamping lever. The clamping lever has a hole, in which the bar or shaft is guided. The hole becomes eccentric in relation to the bar or shaft due to the pivoting of the clamping lever, so that the bar or shaft is clamped.

SUMMARY OF THE INVENTION

The basic object of the present invention is to improve a work table of the type described in the introduction such that the clamping will be reliably preserved even in case of failure of the energy supply, especially the pressurizing agent supply (fail-safe behavior).

To accomplish this object, the work table according to the present invention is characterized in that the locking means is released when the energy supply is switched on and activated when the energy supply is switched off.

Hydraulic oil/fluid is used predominantly for the energy supply in machine tools, and pneumatic energy supply by means of, e.g., compressed air is used less frequently. The locking means is consequently designed according to the present invention such that it fixes the rotary element in the pressureless state. If a pressurizing agent is admitted to actuating cylinders of the locking means, the locking means is released and the rotary element can be rotated. If the pressurizing agent supply fails for whatever reason, the locking means remains fully active. The rotary element cannot rotate inadvertently.

It is, of course, also conceivable to actuate the locking means by means of electromagnets, which are to be supplied with electric energy in this case. The locking means is designed in this case as well such that it is released only when the electromagnet is switched on.

It is common to the locking means known from DE 202 02 998 U1, U.S. Pat. No. 6,457,383 B1 and U.S. Pat. No. 6,001,145 A that they operate by clamping, i.e., in a nonpositive manner. This has the advantage that locking is possible continuously in any desired angular position. However, if continuous locking is unimportant and, in particular, very high torques are to be absorbed by means of the locking means, a positive-locking fixation may also be performed within the framework of the present invention. Hirth rings are especially suitable in this case, because they permit very small angle increments.

An additional actuating member, which further boosts the locking force applied by the restoring member, is preferably provided. This would be especially suitable when the workpiece mounted on the work table is exposed to especially strong machining forces. Even though the locking force is reduced to the locking force applied solely by the restoring member in case of a failure of the rest of the actuating member, this force is sufficient to allow sufficient time for the human operator or the electronic system for an emergency shut-off of the machining, without a dangerous rotation of the workpiece mount occurring during this time.

For example, springs or the force of gravity are used as the restoring member. The actuating members are preferably actuated by pressurizing medium. Hydraulics, in particular, but also compressed air are usually available at all machine tools.

The suitable actuating members are especially annular pistons. These may be led on the outside around the workpiece mount and thus have the greatest possible lever arm and consequently the strongest possible locking force at a predetermined pressure. The annular piston may be designed as a plastic part and press-fit into an annular groove acting as a cylinder housing, so that no separate sealing elements are necessary.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained in greater detail below on the basis of exemplary embodiments shown in the drawings. In the drawings:

FIG. 1 is a vertical sectional view of a first work table having the features of the present invention;

FIG. 2 is a horizontal sectional view of another work table having the features of the present invention; and

FIG. 3 is a view of the work table according to FIG. 2 in a section plane rotated in relation to FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, the work table shown in FIG. 1 has a housing 10 and, as a first rotary element, a pivoting housing 11 mounted rotatably at the housing 10. A face plate 12, at which workpieces can be mounted for machining in the known manner, is mounted rotatably as an additional rotary element at the pivoting housing 11. The pivoting housing 11 is rotatable around a first pivot axis 13 in relation to the housing 10, and the face plate 12 is rotatable around a second pivot axis 14 positioned at an angle in relation to the first pivot axis 13 in relation to the pivoting housing 11. The pivoting housing 11 is mounted at the housing 10 and the face plate 12 is mounted at the pivoting housing 11 by means of prior-art pivot bearings 15 and 16. A respective torque motor 17 and 18 is used as the rotating drive. The particular angular position of the pivoting housing 1 in relation to the housing 10 can be detected by means of a measuring system 19. Another measuring system 20 is used to detect the angle of rotation position of the face plate 12 in relation to the pivoting housing 11.

A locking means 21 is provided to fix the pivoting housing 11 in its angular position in relation to the housing 10. Another locking means 22 is used to fix the angular position of the face plate 12 in relation to the pivoting housing 11. The two locking means 21, 22 have, in principle, the same design and will be described below on the basis of FIGS. 2 and 3.

FIGS. 2 and 3 show another work table, namely, a round table. This has a housing 23 and a face plate 24, which is mounted at the housing 23 rotatably around the axis of rotation 25. The face plate 24 can again be fixed in relation to the housing 23 by means of a locking means 26. This locking means has a design analogous to that of the locking means 21 and 22 for the work table according to FIG. 1, so that it is sufficient to describe below this locking means 26 only in greater detail.

A housing ring 27 is arranged, for example, screwed, on the housing 23. This housing ring 27 has an annular groove 28, into which an annular piston 29 is inserted. The annular piston 29 is made of a plastic and has a press fit in relation to the annular groove 28, so that it is automatically sealed against the annular groove 28. Pressurizing agent, specifically hydraulic oil, can be admitted into a pressure space 32 under the annular piston 29 via a connection hole 30 and an ascending pipe 31. As a result, the annular piston 29 is lifted out of the annular groove. As a result, the annular piston 29 raises a fixed disk 33. An outer edge of a rotating disk 34, which said disk is nonrotatably connected with the face plate 24 and rotates together with same, is arranged on the inner side of the annular piston 29 under the fixed disk 33.

In the lowered state, when the pressure space 31 under the annular piston 29 is pressureless, the fixed disk 33 clamps the rotating disk 34 between itself and the housing ring 27. The face plate 24 is fixed and workpieces mounted on it can be machined. If pressurizing agent is admitted into the pressure space 32, the annular piston 29 raises the fixed disk 33, so that the rotating disk 34 can rotate freely under the fixed disk 33. The face plate 24 can be rotated in this position. As soon as the desired angle of rotation of the face plate 24 in relation to the housing 23 has been set, the pressure is released from the pressure space 32. The fixed disk 33 is lowered by means of suitable restoring members and clamps the rotating disk 34. Suitable restoring members may have the following design:

Weights, for example, in the form of a ring that lies on the fixed disk 33 and is connected with the fixed disk 33 and/or the housing ring 27 in a suitable manner, may be located on the fixed disk 33 in case of work tables in which the disks 33 and 34 are located in a plane that is sloped at a sufficient angle in relation to the force of gravity. If this solution is not sufficient or is even impossible, e.g., when the plane of the disks 33 and 34 is located in the direction of the force of gravity, it is also possible to provide restoring members. It is possible, for example, for this purpose to screw the above-mentioned ring to the annular housing 27 and to provide compression springs between the heads of the screws and the ring, on the one hand, and/or between the ring and the fixed disk 33, on the other hand.

Another variant is shown in FIG. 3. A ring 35 is provided here on the side of the fixed disk 33 facing away from the annular housing 27 and is connected with the annular housing 27 and/or the fixed disk 33 in a suitable manner. An annular groove 36, into which a second annular piston 37 is inserted, is provided in the ring 35 on the side facing the fixed disk 33. This annular piston 37 has exactly the same design as the annular piston 29, so that the same component can be used, which minimizes the manufacturing and stocking costs. The annular piston 37 is again press-fitted in relation to the annular groove 36, so that it is sealed against the annular groove 36.

A pressure space 38 above the annular piston 37 is supplied with pressurizing agent, specifically hydraulic oil, via supply holes 39, 40, 41, 42, 43. Of these supply holes 39 . . . 43, the supply hole 42 can be drilled only from the outside, as can be recognized from FIG. 2. It is therefore closed by a plug 44 toward the outside. Furthermore, the supply holes 40 and 41 are connected with one another via a grommet 45 in order to establish a sealed transition through the fixed disk 33 from the housing ring 27 to the ring 35 for the pressurizing agent supply.

If the pressurizing agent is admitted into the pressure space 38, the annular piston 37 presses the fixed disk 33 in the direction of the housing ring 27. The rotating disk 34 is clamped by the fixed disk 33. This variant has the advantage that the clamping force can be set continuously by varying the pressure in the pressure space 38.

Nonreturn valves, not shown, which ensure that the pressure in the pressure space 28 continues to be maintained in case of failure of the pressurizing agent supply, are provided in the pressurizing agent line in order to achieve the desired fail-safe behavior in this variant.

The variant shown in FIG. 3 can be readily combined with other variants of a restoring element, especially the above-described ones, and it will thus have a clamping force-increasing effect.

Wile specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

APPENDIX

List of Reference Numbers:

-   10 Housing -   11 Pivoting housing -   12 Face plate -   13 Pivot axis -   14 Pivot axis -   15 Pivot bearing -   16 Pivot bearing -   17 Torque motor -   18 Torque motor -   19 Measuring system -   20 Measuring system -   21 Locking means -   22 Locking means -   23 Housing -   24 Face plate -   25 Axis of rotation -   26 Locking means -   27 Housing ring -   28 Annular groove -   29 Annular piston -   30 Connecting hole -   31 Ascending hole -   32 Pressure space -   33 Fixed disk -   34 Rotating disk -   35 Ring -   36 Annular groove -   37 Annular piston -   38 Pressure space -   39 Supply hole -   40 Supply hole -   41 Supply hole -   42 Supply hole -   43 Supply hole -   44 Plug -   45 Grommet 

1. A work table, comprising: a housing; a rotary element mounted rotatably at said housing; a locking means for fixing the particular angle of rotation position of said rotary element in relation to said housing; an actuating member; and a restoring member, wherein said locking means is released by means of said first actuating member when the energy supply is switched on and is activated by means of said restoring member when the energy supply is switched off.
 2. A work table in accordance with claim 1, further comprising an additional actuating member provided to boost the locking force.
 3. A work table in accordance with claim 1, wherein said restoring member is a weight utilizing the force of gravity.
 4. A work table in accordance with claim 1, wherein said restoring member is at least one spring.
 5. A work table in accordance with claim 1, wherein a pressurizing agent is admitted to said actuating member to release said locking member.
 6. A work table in accordance with claim 5, wherein said actuating member is an annular piston guided sealingly in an annular groove.
 7. A work table in accordance with claim 1, wherein said actuating member activates a fixed disk, which is nonrotatable in relation to said housing and cooperates with a disk, which is rotatable but nonrotatable in relation to said rotary element, to fix said rotary element.
 8. A work table in accordance with claim 7, wherein said fixed disk is actuated by a restoring member to fix said rotary element.
 9. A work table in accordance with claim 1, wherein said additional actuating member is an annular piston actuated by a pressurizing agent.
 10. A work table in accordance with claim 9, wherein said annular piston is guided sealingly in an annular groove.
 11. A work table, comprising: a housing; a first rotary element mounted rotatably at said housing; a second rotary element mounted rotatably at said first rotary element; a first locking means for fixing a particular angle of rotation position of said first rotary element in relation to said housing; a second locking means for fixing the particular angle of rotation position of said second rotary element in relation to said first rotary element; an actuating member; a restoring member, wherein said locking means is released by means of an actuating member when the energy supply is switched on and activated by means of a restoring member when the energy supply is switched off.
 12. A work table in accordance with claim 11, wherein a additional actuating member is provided to boost the locking force.
 13. A work table in accordance with claim 11, wherein said restoring member is a weight utilizing the force of gravity.
 14. A work table in accordance with claim 11, wherein said restoring member is at least one spring.
 15. A work tables in accordance with claim 11, wherein a pressurizing agent is admitted to said actuating member to release said locking means.
 16. A work table in accordance with claim 15, wherein said actuating member is an annular piston guided sealingly in an annular groove.
 17. A work table in accordance with claim 1, wherein said actuating member actuates a fixed disk, which is nonrotatable in relation to said housing and cooperates with a disk, which is rotatable but nonrotatable in relation to said rotary element to fix said rotary element.
 18. A work table in accordance with claim 17, wherein said fixed disk is actuated by means of a restoring member to fix said rotary element.
 19. A work table in accordance with claim 18, wherein said additional actuating member is a piston actuated by a pressurizing agent.
 20. A work table in accordance with claim 19, wherein said piston is an annular piston guided sealingly in an annular groove. 